Ideal Gas Law

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Ideal Gas Law

• Just a few examples

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The basic equations

• P pressure (Pa)
• 1 atm 101.3 kPa
• V volume (m3)
• 1 L 10-3 m3
• T temperature (K)
• N number of molecules
• n number of moles
• k Boltzmanns constant
• R Universal gas constant

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Problem 1

• A persons lungs might hold 6.0 L of air at body
  temperature (310 K) and atmospheric pressure (101
  kPa). Given that the air is 21 oxygen, find the
  number of oxygen molecules in the lungs.
• 2.9 x 1022 molecules

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Problem 1 solution
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Solving Ideal Gas Law problems

• IGL problems are similar to conservation law
  problems.
• You evaluate P, V, T, and N or n before and
  after.
• Usually, not every thing is changing.
• Set the things that do not change on one side of
  the equation and every thing that does change on
  the other.

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Problem 2

• A cylindrical flask is fitted with an airtight
  piston that is free to slide up and down. A mass
  rests on top of the piston. Contained within the
  flask is an ideal gas at a constant temperature
  of 40C. Initially the pressure applied by the
  piston and the mass is 137 kPa and the height of
  the piston above the base of the flask is 23.4
  cm. When additional mass is added to the piston
  decreases to 20.0 cm Find the new pressure
  applied by the piston.

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Problem 2 solution

• What changes in the problem?
• P, V
• What stays the same?
• N (or n), T